Permeation of bile acids across artificial lipid membranes and Caco-2 monolayers

The permeation behavior of free bile acids (BA) with different numbers of hydroxyl groups as well as of the glycine and taurine conjugates was studied in vitro using artificial lipid membranes and Caco-2 monolayers. The transport across artificial lipid membranes depends strongly on the lipophilicity of the BA applied. Free BA permeated to a higher degree than the: conjugated derivatives. The taurine conjugate was transported only to a very low extent. A distinct influence of the pH value in the donor medium on the permeation of the BA was observed. The transport rate decreased with increasing pH. Using Caco-2 monolayers, it was found that only unconjugated BA could permeate to a higher extent.